Controlling the selectivity and stability of proteins by new strategies in directed evolution: the case of organocatalytic enzymes.

The directed evolution of functional enzymes as catalysts in organic reactions has emerged as a powerful method of protein engineering. This includes the directed evolution of enantioselective enzymes as pioneered by the author. In recent years the challenges in this new area of asymmetric catalysis has shifted to solving the problem of probing protein sequence space more efficiently than before. Iterative saturation mutagenesis (ISM) is one way of addressing this crucial question. This chapter reviews the concept of ISM and its application in controlling the enantioselectivity and thermostability of enzymes, specifically those that have an organocatalytic mechanism. Illustrative examples include the directed evolution of lipases, Baeyer-Villigerases and epoxide hydrolases.